Photographic emulsion



April 13, 1943. A. MAREIS 2,316,268

PHOTOGRAPHIC EMULSION Filed Nov. 14, 1959 4m 20 4o 60 e0 oa eq 40 60 so 00 2a.

1 emudson wit/a s enszjtzln q'. dye 2. emulu'on with supersemtizer 3 emulaon with mixture of senu'adzakgg' d e and supersen a'nzer fidfons Mafia/'6 INVENTOR I BY HIS ATTORNEYS Patented Apr. 13, 1943 ICE PHOTOGRAPHIO EMULSION Alfons Marcia, Dessau, Germany, assignor, by mesne assignments, to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application November 14, 1930, Serial No. 304,300

3 Claims.

This invention relates to photographic emulsions and-more particularly to supersensitized photographic silver halide gelatin emulsions.

It has previously been proposed to increase the intensity of optical sensitization of certain cyanine dyes in the production of sensitized photographic emulsions by adding a second sensitizing dye which acts on the optical .sensltizer as a so-called supersensitizer. The dye Pinaflavol from a-methyl-pyridine-alkyl-iodide and p-dimethylamino-benzaldehyde was named as a supersensitizer.

It is an object of the invention to provide a novel supersensitized silver halide emulsion.

A further object is a novel process of sensitizing.

Still further objects of the invention will appear from the detailed specification following hereinafter.

I have found that the optical sensitization with 2.2'-monomethinecyanine dyes of the following general formula:

is materially increased by employing as so-called supersensitizers the non-quaternary styryl compounds of nitrogen-containing heterocyclic bases with p-dialkylaminobenzaldehydes of the following formula:

In this formula A stands for any suitable nitrogen-containing heterocyclic ring system,

n is 1 or 2,

R1 and R2 are identical or difierent alkyls.

These supersensitizers are not in themselves dyestuils and do not resemble dyestuffs. They are Germany November 24, 1938 added to the sensitizing dye or they may be added to the emulsion separately. Their concentration is in most cases materially lower than that of the sensitizing dye. In the amount in which they are employed they have no sensitizing action per se. A

The single figure shows the action of the supersensitizer. The diagram 1 shows the sensitization of the quinopseudocyanine dye according to Example 1 for itself. The diagram 2 shows the spectral sensitivity of the emulsion with the added supersensitizer according to Example 1. This diagram corresponds exactly with the spectral sensitivity of the silver halide emulsion without any addition. Diagram 3 shows the spectral sensitivity of the emulsion containing the sensitizer and the supersensitizer.

The advantage of the supersensitizer according to this invention which is a non-quaternary feebly dyed compound in contrast to the quaternary styryl dyestuff resides in the fact, that smaller quantities may be employed which makes for a better fastness of the sensitization with an at least equal intensity of the sensitization compared with that obtained by employing a quaternary styryl dye. Furthermore, it is advantageous that the new supersensitizers in themselves do not sensitize a silver bromide or silver chloride emulsion to any practical extent or only in the region of the very short wave lengths. In contrast thereto the quaternary dyes, for instance Pinailavol are well known to be good sensitizers for green and yellow. The supersensitizers of this invention therefore offer the advantage of a steep incline in sensitization. This allows the films prepared from the emulsions to be treated in bright darkroom light even if the emulsions are the modern emulsions of high sensitivity (for instance 21/10 din). A specialthird advantage of the new method of sensitization is their high stability against stabilizers of all kinds-especially against the organic stabilizers for instance those of U. S. Patent No. 1,758,577'which are now usually employed.

The production of the non-quaternary styryl compounds is described in Berichte" 39, (1906), page 27 to page 49, and "Berichte" 27, (1894), page 1969.

The following examples -illustrat'e the invention: 0

Example 1 To l. kilo of a medium sensitive silver halide gelatin emulsion produced according tothe ammonia process with about 2 per cent of silver iodide of fine grain and steep gradation. there are added in the form of a methanol solution (1 in 10,000) 20 mg. of the sensitizers of the forand 2 mg. of the weakly-yellow sensitizer of the following composition:

Example 2 To 1 kilo of the emulsion described in Example 1 there are added for the purpose of sehsitization frstly 2 mg. of the supersensitizer described in Example 1 and then 30 mg of the pseudocyanine of the following formula:

To 1 kilo of a supersensitive emulsion containing 3 per cent of AgI and produced accordin to the ammonia process there are added 3 mg. of the supersensitizer described in Example 1 and 30 mg. of the. pseudocyanine of the following formula:

An emulsion of this kind is extremely well suited as a supersensitive ortho-chromatic motion picture film emulsion.

Example 4 To 1 kilo of a supersensitive emulsion containing 4 per cent of AgI there are added 3 mg. of a supersensitlzer oi the formula 8 Gig (Loreen-QM N I and 30 mg. of a dye of the formula cm l N J 6.1:.

Example 5 To 1 kilo of the emulsion described in Example 3 there are added 2 mg. of a supersensitizer of the following formula and 30 mg. of the-dyestuif of the following for- C 1H; Example 6 To 1 kilo of the emulsion'described in Example 1 there are added 2 mg. of a supersensitizer of the following formula s @Ji-CH=CHCH=CHON and 30 mg.- of the pseudocyanine described in Example 1.

Example 7 To 1 kilo of a medium sensitive emulsion of steep gradation containing ,3 per cent of AgI there are added 2 mg. of the supersensitizer according to Example 1, 10 mg. of N.N'-diethyipseudocyanine iodide plug 20 mg. of N.N'-diethyl 6' methyl selenopseudocyanine iodide (formula see Example 4).

I claim:

1. Photographic silver halide gelatin emulsion containing a 2.2'-monomethine cyanine and a non-quaternary styryl compound of the following general formula R R2 wherein A stands for, a nitrogen-containing heterocyclic ring system; n is 2; R1, R2 is alkyl. 2. A photographic silver halide emulsion as defined in claim 1 wherein the non-quaternary styryl compound has the following formula:

3; A photographic silver halide gelatin emulaion containing the following cyanine dye:

and a non-quaternary styryl compound of the following formula:

. mops mus. 

